Modulation of exchange bias in Py/IrMn films by surface acoustic waves

We investigate the surface acoustic wave (SAW) modulation of the exchange bias field (H_EB) in Py/IrMn films deposited on LiNbO₃ substrates. We measured the anisotropic magnetoresistance (AMR) of the multilayer film when continuous SAW or pulsed SAW were applied and obtained H_EB. With continuous SAW, the H_EB decreases continuously with power. While in the case of pulsed SAW, the H_EB first decreases and then stabilizes. Compared to pulsed SAW, the thermal effects from the continuous SAW lead to the continuous decrease of H_EB at higher SAW power, which is verified by the measurement of H_EB at different temperatures and input currents. Furthermore, our results show that pulsed SAW can effectively avoid thermal effects. The decrease of H_EB at smaller power in both continuous and pulsed SAW is mainly due to the SAW-induced dynamic strain field, which leads to a small perturbation in the magnetic moment of the FM layer. Combined with the AMR values measured at different angles during the saturation field, we believe that the SAW-induced dynamic strain field causes a 15° angle between the magnetic moment and the easy axis. Our experiments provide a different approach to manipulating H_EB, opening up a potential avenue for future manipulation of antiferromagnetic moments.